Questions tagged [electric-fields]

For questions that utilize the concept of electric fields (commonly denoted by the letter E), or for questions whose answers likely involve electric fields. More specific than the [electricity] tag, as questions about the phenomenon & theory of electricity do not necessarily involve the discussion of fields.

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31 views

Does constructive interference automatically imply bright fringes at all times?

Suppose two waves interfere constructively at some point, in a double slit experiment set-up. This essentially means that the two waves have their peaks and troughs in sync with each other, and there ...
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1answer
19 views

How is electric flux density independent of medium?

I understand that the scalar quantity, electric flux, $\phi$, is dependent on the medium. Also, mathematically, I understand how vector quantity electric flux density, $\mathbf{D}$, is independent of ...
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Complex electric field in second order polarization

I am reading an introductory article on nonlinear optics. Here is what the part that's troubling me says: $$\tilde E(t) = Ee^{-i\omega t} + \text{c.c} $$ When this electric field is incident on a ...
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1answer
39 views

Interaction between electron and electric field

Let consider that we are using parallel plates to create electric field. And let assume that there are small holes in both the plates (holes on both the plates are aligned). Now if we bring a electron ...
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1answer
25 views

How does the electric field pattern looks like when current is moving inside the conductor and why this field is uniform?

We know that electric field is uniform inside a normal electric circuit consisting of some battery source and a conducting wire , $\mathrm{E}$ will be $\mathrm{E=V/d}$ , but I cannot think of a reason ...
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1answer
192 views

Behavior of the electric field of an incoherent light wave

If I am not mistaken, an incoherent light wave is a light wave made out of waves with random phases: it consist of photons with random phases. Now I am wondering what we would see if we would ...
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2answers
490 views

Quantum correlation functions of the electric field

The first order correlation function for one mode (up to normalization) is definied as: $$g^{(1)}=\langle a^\dagger(t) a(t+\tau) \rangle$$ The second order: $$g^{(1)}= \langle a^\dagger(t)a^\dagger(t+\...
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22 views

Charged particles simulation in different planes

I have been trying to figure out an analytical/numerical method to calculate the following: there is a charge distribution (gaussian) of positive charges in a plane, whereas there are negative charges ...
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2answers
74 views

What is the electric field in a region of constant potential?

I am working on a problem set on electrostatic potential and there is this one particular question posed that states "The electric field in a region of constant potential is?". The answer ...
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2answers
90 views

Why does near-field attenuate at $\frac{1}{r^6}$?

So far-field makes intuitive sense to me, it attenuates at $\frac{1}{r^2}$ much like gravity. This is just common sense since the area for the surface of a sphere relative to its radius has a $r^2$ ...
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44 views

Electric field of a configuration of five parallel infinite slabs of dieletric materials

I am having a hard time trying to figure out how to proceed in order to calculate the electric field of a configuration of five slabs of dieletric (insulating) material (actually one of those is ...
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1answer
1k views

Neutral conductor and charged insulator brought near each other

What happens when a charged insulator is placed near an uncharged neutral metallic conductor? I know it attracts each other because of charging by induction (electrons redistribute). But would the ...
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84 views

Connection between quaternions and electromagnetism

Consider the multiplication of two quaternions, which can be written as a matrix equation: $$ xy = \begin{pmatrix} x_0 & -x_1 & -x_2 & -x_3 \\ x_1 & x_0 & -x_3 & x_2 \\ ...
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74 views

What is the precise definition of *direction* of current and of current element for a conductor?

The Biot–Savart law states that magnetic field due to an elemental cylindrical system through which a constant current $I$ is passing at a point $r$ distance away is given by $$d\vec{B}=\frac{\mu_o}{4\...
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1answer
646 views

How to calculate the potential energy of an $H_2$ molecule?

From left to right, electron $e_1$, $e_2$ and proton $p_1$, $p_2$. $r_0=0.529nm$ The total energy is sum of energy require to bring each particle to its place. Take the place of $e_1$ is zero ...
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6k views

Electric Field "at" the surface of a conductor

It has been pointed out to me that the Electric field exactly on the surface of the conductor is conventionally taken to be $E=\frac{\sigma}{2\epsilon_0}$; does this come from taking the midpoint of ...
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45 views

What is the definition of direction of current?

Wikipedia defines the direction of current as: The direction of conventional current is arbitrarily defined as the direction in which positive charges flow. But suppose a region where there is a non-...
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1answer
2k views

Diffusion and Drift currents in forward bias

Why do the current in diode in forward bias configuration called "Diffusion current" even if this current is a resultant of external voltage supply which create electric field in diode ,hence should ...
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1answer
150 views

Why is the field inside a capacitor not the sum of the field produced by each plate?

In this answer by David Z, we can read, When discussing an ideal parallel-plate capacitor, $\sigma$ usually denotes the area charge density of the plate as a whole - that is, the total charge on the ...
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1answer
35 views

Does electrically neutral mean the potential is zero?

I don't know if this is a silly question, but I have a homework problem that tells me a line charge is electrically neutral at time $t=0$. I was calculating the potential from the definition $$ V(\...
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2answers
62 views

Why is the magnetic field around a straight current-carrying wire in concentric cirlces?

I have a question that, why are the magnetic field lines around a straight current carrying wire in the form of concentric circles? If the wire is carrying current, it is acting like a magnet. So ...
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3answers
103 views

Is it possible to find the proportionality constant in Gauss's law for an electric field without knowing Coulomb's law?

Using the definition of electric flux, and knowing that the electric flux through a closed surface is proportional to the charge enclosed (that proportionality constant being $ \frac{1}{\epsilon_0} $)....
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1answer
28 views

How would one calculate the electric field produced by a piezoelectric device in response to a sound wave?

So the governing equations of piezoelectricity are: Where E is the electric field, D is the displacement field, S is the strain, and T is the stress. Say I have a piezoelectric device where the ...
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44 views

Total Energy of an electromagnetic wave

This question may sound stupid. But why when we calculate the total energy density (energy/volume), carried by an electromagnetic wave $u_T$, we add both $u_B$ + $u_E$. Where $u_B = \frac{B^2}{2\mu_0}...
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Field Theory: Electric Field

I am a grade 12 student, and we are learning electric flux. We covered electrostatic forces and, now we are on electric flux. We defined electric flux as the total number of lines of force passing ...
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2answers
54 views

$\delta(t) = E(t) e^{-i[\nu t + \phi(t)]}$: the "positive frequency part of the electric field"

I have the time dependence of the electric field $A(t)$ written in terms of the amplitude $E(t)$ and phase $\phi(t)$ as $$A(t) = E(t) \cos[\nu t + \phi(t)].$$ I am told that this varies slowly in an ...
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371 views

Cylindrical coordinates of a ring

A classical problem for electromagnetism students is the calculation of the electric field on the central axis of a ring. It can be solved in many different ways, but I got stuck with the pure ...
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51 views

How can there be zero electric field in the marked region (in the image) in the conductor?

as the marked region is nearer to surface with positive charge density should there be a net electric field instead of 0?
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2answers
24 views

$A(t) = E(t) \cos[\nu t + \phi(t)]$ varies slowly in an "optical period" of $2\pi/\nu$?

I have the time dependence of the electric field $A(t)$ written in terms of the amplitude $E(t)$ and phase $\phi(t)$ as $$A(t) = E(t) \cos[\nu t + \phi(t)].$$ I am told that this "varies slowly ...
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5answers
94 views

The electric field formula $E=F/q$

If we follow the formula $E=F/q$ it says that when the force is bigger the electric field is bigger as well but if the charge on which the force is being exerted to bigger the electric field is ...
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1answer
40 views

Direction of electric field while taking infinity

A positive charge $q$ is placed somewhere. So electric lines of forces will be radially outward from this charge. While defining potential at a distance $r$ from $q$, we say it is the work done to ...
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1answer
36 views

Can we give a desired direction to the electric field by connecting the wires to one terminal having some potential?

Let's say we have a battery and one wire is connected to the one terminal having let's say some positive potential and other end of the wire is connected to the plate which is from one side it is ...
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1answer
80 views

I am not able to convince myself with the gauss law, explain why the situation below shouldn't have non-zero flux?

I have drawn an image of a spherical surface and positive charge outside it. As the positive charge is outside the sphere the electric field incident at every small surface is different from the other ...
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1answer
55 views

Does the number of electrons colliding in wire get double as the length of wire gets doubled?

Does the number of electrons colliding in a wire get doubled when length of wire is made twice with its area of cross-section remain constant. My calculations for this are:- For wire of length $L$: ...
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0answers
201 views

Why would this integral of the time derivative of the magnetic field equal zero?

I'm reading electrodynamics physics notes that describe a 1-dimensional cavity of length $L$. The cavity is said to lie along the $z$-axis from $-L$ to $0$. There is a reflective mirror at $z = 0$, ...
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25 views

Electric field in a supercapacitor/electrophoretic system

I'm trying to understand how the application of electric potential acts in between two electrodes in a capacitor-like structure (parallel plates or cylindrical electrodes) immersed in a solution with ...
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0answers
55 views

Equation of path traced by a charged particle in time varying magnetic field

Is there anyway to figure out the equation for trajectory of a charged particle in a magnetic field(which varies with time) increasing inside the plane of the screen, the particle is outside the ...
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5answers
515 views

How does an electric dipole lose its energy while aligning with a uniform electric field?

How does an electric dipole lose its energy while aligning with a uniform electric field: through heat or light?
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2answers
39 views

Why charge induce inside doesnt depend on what the outer potential is, in a conductor?

Let's suppose we have a conducting shell which has an outer radius $R$ and inner radius $r$. A charge is kept inside (not at the centre). We know that a charge will be induced in both surfaces. But ...
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63 views

Why would this integral of the time derivative of the electric field equal zero?

I'm reading electrodynamics physics notes that describe a 1-dimensional cavity of length $L$. The cavity is said to lie along the $z$-axis from $-L$ to $0$. There is a reflective mirror at $z = 0$, ...
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3answers
1k views

What happens to the potential of electron?

When we let the electron move freely in an electric field, the electric potential of electron must decrease but the electron moves opposite to the field so do we say that it's electric potential is ...
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1answer
26 views

Why is the Electric Field from Point Charges vs a Continuous Line Different?

I was doing some calculations regarding the difference between the electric field generated by point charges vs a continuous line of charge (trying to come up with a cool/challenging physics problem), ...
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1answer
21 views

Electric field inside a non-uniformly charged conductor

With Gauss's Law, if we take a uniformly charged hollow sphere for instance, the electric field inside the hollow sphere is 0 because there is no charge inside. However, what if this sphere is not ...
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0answers
59 views

Electrical conductivity/resistance of gas or vapor in an electrostatic field at normal temperature and pressure

For liquids (e.g. liquid metal and water), I could find their electrical conductivities (unit in S m$^{-1}$) or resistances in the CRC handbook. Also, I noted that equations for calculating the ...
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1answer
68 views

Relativity and Electromagnetism: why doesn't every current-carrying wire generate a perpendicular electric field?

I was looking at Purcell's derivation of a current-carrying wire's magnetic field using the Lorentz transform, and noticed something which bothered me. It assumes that the distance between positive (...
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2answers
188 views

Electric Field stays the Same even though Distance Increases?

I was working on physics homework and came across this multiple choice question. Two metal plates of area A and separated by a distance d are placed in parallel near each other to form a capacitor ...
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2answers
538 views

What happens with the divergence of maxwell stress tensor when EM fields in vacuum?

The conservation momentum can be derived from the total electromagnetic force on the charges in volume $V$ and is written in this way: $$ \frac{d\vec{p}_{mech}}{dt} + \frac{d}{dt} \int_V (\vec{E}\...
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1answer
833 views

How do I calculate the surface potential of a conductor given a charge distribution?

I have tried the conventional definition but since there is a charge density at the point we want to calculate the potential at, it turns out to be infinity. Now, i dont know how to calculate the sum ...
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3answers
161 views

How does the battery create an electric field inside the conducting wire connected to its terminal?

In books, it is not explained exactly how the battery creates an electric field inside the wire. Also, is that the electric field inside the wire only or is it present outside the wire as well?
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1answer
170 views

Expansion of the derivatives of the electric and magnetic fields

I'm reading electrodynamics physics notes that describe a cavity of length $L$. The cavity is said to lie along the $z$-axis from $-L$ to $0$. The electric field is polarized in the $x$ direction and ...

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